(i) Field of the Invention
The present invention relates to a sealing material for a liquid crystal display panel and the liquid crystal display panel using the sealing material.
(ii) Description of the Prior Art
In general, liquid display panels can be roughly classified into a simple matrix type liquid crystal display panel which can be formed by integrally sticking a pair of substrates provided with striped transparent electrodes so as to keep a certain space between these substrates, and then holding a liquid crystal composition between the substrates; and an active matrix type liquid crystal panel which can be formed by integrally sticking a pair of substrates so as to keep a certain space therebetween, at least one of the pair of substrates being equipped with a liquid crystal control element such as TFT, MIM or a diode, and then holding a liquid crystal composition between the substrates. In particular, the active matrix type liquid crystal panel is excellent in the control performance of contrast and half tone, and for this reason, it has been used in a color image display or a projection type display.
When an active matrix substrate equipped with an element such as TFT or a diode and bus line electrodes is integrally stuck to an opposite electrode substrate provided with a glare protecting pattern for protecting the element on the active matrix substrate from intensive light, these substrates are required to be aligned with high precision in order to prevent adjacent pixels from mixing and to inhibit contrast and TFT properties from deteriorating.
Heretofore, as a sealing material for sticking the pair of substrates so as to keep the certain space therebetween, a thermosetting epoxy resin has been used.
However, in the case that the thermosetting epoxy resin-based sealing material is used, a pressurizing step and a heating step which take a long period of time are necessary to set the sealing material by which the substrates are integrally stuck, and therefore there is the problem that the employment of the thermosetting epoxy resin-based sealing material is not suitable for continuous mass production. In addition, when the pair of substrates are different from each other in materials, the alignment tends to deviates owing to the difference of thermal expansion coefficient between the substrates, and the thickness of a cell is uneven, so that the display quality of the obtained liquid crystal display panel deteriorates inconveniently.
In recent years, there has been reported a liquid crystal display panel using an ultraviolet-setting resin as another sealing material (Japanese Patent Application Laid-open Hei 1 No. 243029).
However, the utilization of the ultraviolet-setting resin leads to some drawbacks. That is, the ultraviolet-setting resin has high moisture permeability, and when an ionic or an unreacted material is dissolved in the liquid crystal, the orientation of the liquid crystal is disordered in the vicinity of a sealed portion, so that the liquid crystal composition deteriorates and thus its electrical resistance noticeably declines. Furthermore, the ultraviolet-setting resin is inconveniently weaker in adhesive strength to the substrates than the thermosetting epoxy resin-based sealing material. Hence, any sealing material having both reliability and adhesive strength has not been present.